1. Field of the Invention
The invention relates in general to a voltage-current characteristic generator, and, in particular, to a voltage-current characteristic generator able to emulate voltage-current characteristics of an electric and/or electronic device, such as a battery or a semiconductor, connected to a device being measured such as an electronic device or a power supply.
2. Related Art
There is the need for a device to perform emulation of voltage-current characteristics of electric and/or electronic devices. For example, if there were a device that emulates the characteristics of a desired light-emitting diode element in order to confirm the operation of an LED driver that supplies power to a light-emitting diode element that is used for light-emitting diode illumination, the LED driver could be designed and manufactured efficiently. Moreover, if there were a device that emulates the voltage-current characteristics of a rechargeable battery, which changes depending on the operating time and environment, then it would be possible to design and manufacture mobile electronic devices efficiently. A voltage-current characteristic emulating device is disclosed in Japanese Unexamined Patent Application Publication 2010-151592 (“JP '592 reference”) as an attempt to provide an electronic load device or load emulating device that is a portion of the functions of a device for emulating such voltage-current characteristics.
The JP '592 reference describes achieving the diode characteristics set forth in FIG. 2 thereof through a voltage source or current source. However, when an electronic load 1602, which uses a voltage source, is connected to a device under test (DUT) 1604, which has a low output impedance, in the circuit 1600, as shown in FIG. 16A, the operation of the electronic load 1602 may become unstable in regions, such as region R1 in FIG. 16B, wherein the absolute value of the slope of the voltage-current curve is low, and thus cannot provide the desired characteristics to the DUT 1604 (such as, for example, an LED driver) because the voltage-current values are not stable. In this example, the electronic load 1602 is controlled by a controlling portion 1610 through feedback so as to apply the desired voltage and current to the DUT 1604 based on the voltage value applied to the DUT 1604 (as read out from a voltmeter 1608) and the current value that flows in the DUT 1604 (as read out from an ammeter 1606).
Moreover, when an electronic load 1702, which uses a current source, is connected to a DUT 1704, which has a high output impedance, in the circuit 1700 as shown in FIG. 17A, the operation of the electronic load 1702 becomes unstable in regions, such as regions R2 and R3 in FIG. 17B. In this example, the absolute value of the slope of the voltage-current curve is large, and thus cannot provide the desired characteristics to the DUT 1704 (such as, for example, an LED driver) because the voltage-current values are not stable. In this example, the electronic load 1702 is controlled by a controlling portion 1710 through feedback so as to apply the desired voltage and current to the DUT 1704 based on the voltage value applied to the DUT 1704 (as read out from a voltmeter 1708) and the current value that flows in the DUT 1704 (as read out from an ammeter 1706).
In these examples, the diode characteristics in FIG. 16B and FIG. 17B show the diode characteristics when viewed from the electronic loads 1602 and 1702, and because the electric currents that flows in from the outside are represented by negative values, they are in a form that has been inverted in the up/down direction from that of the graph in FIG. 2 of the JP '592 reference. The other characteristic graphs in the specification are shown in the same way.
In Japanese Unexamined Patent Application Publication H08-262069 (“JP '069 reference”) a voltage-current characteristic measuring device that can be used as a high precision voltage source or current source is disclosed. This circuit is assumed to be used as a voltage source or current source for a load in a region wherein stabilized operation is possible.
As such, the known prior art does not go beyond achieving emulation of voltage-current characteristics in regions that are limited in advance and slopes that are limited in advance. Therefore there is a need for a system that overcomes the problems stated above.